This invention relates to a hypodermic syringe assembly.
Many different types of hypodermic syringe assemblies are known in the art. Most of these assemblies use an elongate dispensing container in conjunction with a piston which is longitudinally movable within the container. Additionally, many of these syringe assemblies include a separate plunger mechanism. Examples of such prior art syringe assemblies include U.S. Pat. No. 2,586,068 to Lockhart; U.S. Pat. No. 2,688,325 to Lockhart; U.S. Pat. No. 3,874,382 to Nogier et al; U.S. Pat. No. 4,677,980 to Reilly et al and U.S. Pat. No. 3,672,368 to Schwarz.
When designing a syringe assembly it is sometimes desirable to have the plunger and piston capable of moving as a unit in both directions within the container. The Schwarz patent, in FIG. 5 thereof, discloses one method of doing this. The Schwarz patent uses claw shaped elastomeric extensions to engage a circumferential groove in a plunger so that the plunger and the piston can move together within the syringe container.
Although the arrangement shown in Schwarz creates good attachment between the plunger and the piston, it is an expensive arrangement due to the materials used.
Depending upon the application to which a syringe assembly will be used it may be desirable to have parts of the assembly disposable while other parts are not. If portions of a syringe assembly are disposable it is of course desirable to have these portions relatively inexpensive to manufacture. Further, any portions of the assembly which are to be reused must be kept from contact with any material which must be sterile.
Accordingly, it is a purpose of this invention to provide a hypodermic syringe assembly in which the piston is capable of locking to a plunger.
Yet a further purpose of this invention is to provide such an assembly which is relatively inexpensive to manufacture.
Another purpose of the invention is to provide such an assembly wherein the syringe container and piston are disposable and wherein the plunger to be used therewith is meant to be reused.